Anyways, your build will "work" but there are a few things worth considering...

You're planning to build a BD based machine, but we have no way of knowing how well BD will be. I'm assuming you're an AMD fan, but the prelminary reviews for BD suggest that it's worse than a comparable Sandy Bridge machine. If you're going to be spending on a top of the line machine, why not go for something which will give you the best performance period?

Also, with a machine like that, you should really consider getting an SSD. The Crucial M4 is a good one.

running 4 double wide slot cards is difficult, 3 out of 4 of them will suck hot air from the back plate of the one in front and the platform will be noisy. Had 3 nvidia cards and all of them were running at 60% fan speed, and with default profile from EVGA precision they are noisy. Speaking from my own experience. Even with good lateral cooling the system will be noisy. In order for the 4th card to be double wide you will need an Extended ATX case, something for servers otherwise will not fit as most cases don't have the necessary space if the power supply is bottom mounted. So 3 double wide and a single slot is doable on a regular ATX case but with compromise of noise.

Yah, I wouldn't suggest actually running 4 cards (at least on air), just saying that if he plans to run a single dual-gpu card he doesn't need a UD7, the lesser UD series boards will do just fine. If he does go UD7 might as well go with 2 top end single GPU cards.

OK let's face it, you're going all out almost without respect for budget. Intel's X79 chipset is due out (next month? more than one article I've read says Nov.) and is going to be THE enthusiast chipset of choice for the immediately forseeable future - more memory lanes and DDR-2800 capable, something like 3x or 4x as much bandwidth thru the system, blah blah this yada yada that, it's going to make a current 67/68 Sandybridge look positively neutered. If I were dropping that coin, I'd hang in.

OK let's face it, you're going all out almost without respect for budget. Intel's X79 chipset is due out (next month? more than one article I've read says Nov.) and is going to be THE enthusiast chipset of choice for the immediately forseeable future - more memory lanes and DDR-2800 capable, something like 3x or 4x as much bandwidth thru the system, blah blah this yada yada that, it's going to make a current 67/68 Sandybridge look positively neutered. If I were dropping that coin, I'd hang in.